THE EFFECT OF THE PREVIOUS CROP ON THE GROWTH, NITROGEN UPTAKE AND YIELD OF WINTER BARLEY INTENDED FOR MALTING

Winter barley which received a range of nitrogen rates, was grown at R othamsted as a test crop after winter oats, winter barley, winter bean s, oilseed rape or potatoes, to compare the effects of previous crop o n growth and N uptake. In the autumn following the first year crops, t he largest amount of residual inorganic N found in the soil was after potatoes, the smallest after oats. Throughout the second season the he aviest crops of barley, which also contained the most N, were after po tatoes, and the lightest were after barley. To produce grain with a N concentration of less than 1.8 % N (w/w, dry wt), acceptable for malti ng, it was found that not more than 75 kg N ha-1 after barley and 125 kg N ha-1 after oats, 100 kg N ha-1 after beans and 50 kg N ha-1 after rape or potatoes could be applied. The results demonstrated that barl ey of acceptable quality for malting can be grown after a break crop, providing that the rate of N fertiliser is suitably adjusted to take a ccount of the residual fertility, but the results do not suggest that residual soil N affects the grain N concentration differently to N app lied as fertiliser early in the season.